Join Date: Aug 1998
Location: Waldorf Md. USA
If the motor is definitely a 1991, it should be a one piece rear main seal motor. If so, it needs a particular flywheel (flexplate if you wish) If he used the flywheel off your 1984 305, that is definately the problem, even though I thought GM changed the bolt patterns on the one piece flywheels. I could check for sure if you want in the morning. If he used a flywheel off a later model, one piece seal, 305...it should work. It is the same as the late model 350's.
Hope this helps, if you have any other questions you are welcome to e-mail me directly.
Advanced Automotive Machine